ExoMol line lists: LXXI the rovibrational quadrupole spectrum of N2

Abstract

Molecular nitrogen is expected to be abundant in many planetary atmospheres, but its ground-state spectrum is intrinsically weak, making remote detection challenging. Comprehensive line lists are presented for electric quadrupole transitions within the ground electronic state of all three stable isotopologues of molecular nitrogen: 14N2, 14N15N, and 15N2. The TRINITY line lists are generated within the ExoMol framework using the Duo nuclear-motion code from a high-accuracy direct-potential-fit potential energy curve and an ab initio quadrupole moment function, including Born–Oppenheimer breakdown corrections where required. Rovibrational calculations were extended to dissociation (v ≲ 60) and high rotational excitation (J ≤ 80), with high-overtone transitions affected by numerical artefacts excluded. Simulated spectra and partition functions confirm the physical consistency of the resulting line lists and demonstrate their suitability for modelling nitrogen-rich atmospheres at temperatures up to 5000 K. The TRINITY line lists are available from the ExoMol database at www.exomol.com.